1. Field of the Invention
The present invention is related to salvage drums, or over-pack containers, that are adapted to receive industrial chemical drums. These over-pack containers are used to transport and store leaking and otherwise damaged drums containing toxic materials to prevent the contamination of the environment. In particular, the invention is related to rotationally molded salvage drums and lids produced from polyethylene.
2. Description of the Prior Art
Rotationally molded polyethylene salvage drums, or over-pack containers, adapted to contain standard industrial chemical drums are known in the art. An essentially straight-sided, rotationally molded cylindrical polyethylene container adapted to accommodate a 55 gallon industrial drum, to which a flat circular cover can be secured by heat welding, has been used to demonstrate the feasibility of permanently encapsulating the contents for storage. This configuration is not adapted to the use of conventional closure devices, and requires special equipment and handling techniques to seal the cover to the over-pack container, and can not be opened or reused.
A commercially available rotationally molded polyethylene salvage drum has been produced which has a cylindrical sidewall that is tapered inwardly to form a neck portion that extended upwardly and terminated in an integral outwardly extending flange. A generally flat or contoured cover of essentially the same outside diameter as the drum flange is adapted to be secured to the drum by a variety of conventional means, including a conventional metal ring clamp, or nuts and bolts; alternatively the cover is permanently affixed by spin welding, a process in which the cover is rotated against the drum flange until the frictional effects soften and melt the polyethylene surfaces sufficiently to produce a permanent fluid-tight bond. This configuration, while a significant improvement over the straight-side over-pack container, suffered from certain drawbacks in manufacture and use. The smooth-sided containers were also difficult to move with forklift machines and other drum lifting devices. Under certain impact conditions, the metal ring clamp and gasket sealing could fail and permit leakage of liquid contents. The generally uniform diameter of the salvage drums did not permit stacking of the empty drums for storage or shipment. Finally, the flat or single thickness top was subject to deflection upon severe impacts.